Devices of this type have been described, for instance, in German Patent Disclosure No. 32 39 379. Here a collimator device made of glass is used. This collimator device must retain its given configuration when installed. It would be rendered useless long before actually being destroyed, for instance, if the geometrical longitudinal axis of the X-ray beam no longer coincided with the part of the optical axis which is adjusted to coincide with the longitudinal axis by means of a mirror. It would also be unsatisfactory if the through holes described in the patent disclosure no longer run parallel to the geometrical longitudinal axis of the X-ray beam. Similarly it would also be detrimental if the collimator glass body was scratched, because the illuminated area could no longer be so clearly seen etc.
The device described in the German Patent Disclosure is an arrangement wherein the collimator glass body is not exposed to such dangers because a coating is laid on a through hole and, thus, the test specimen can never come into contact with the glass body.
There are, however, measuring devices of this type in which the test specimen to be measured is positioned, either under its own weight or by means of plasticine or similar means, on the top side of a stage or supporting means. After the test specimen has been placed on a stage, the stage is raised within a housing until a test specimen has been driven from below to the correct distance from the glass body. Seen from the viewpoint of Patent Disclosure No. 32 39 379 such measuring devices are upside down. The principle part, which can be moved over large distances, is a stage on which the test specimen lies. The test specimens lying on the stage can be of different heights. If measurements are to be made on a high object, the table must stop at a greater distance from the glass body than the case for thinner test specimens.
As is the case for most measuring devices of this type, the stage here is also not moved manually. Rather, the displacements are motor-driven via computer software.
As with a microscope, fine adjustments must be made by hand and eye. The dimensions of the test specimens can vary immensely from, for example, foils of a few tenths of a millimeter thick to spectacle frames, and can, thus, be extremely light or extremely heavy. Specimens weighing only one gram can be considered heavy in this area of technology.
If, due to error, the stage is driven too high, then, the specimen can come into contact with the collimator device embodied by the glass body and cause it to be scratched or can be pressed against the collimator device such that its geometry is no longer correct or it it completely destroyed.